We describe a near-field ellipsometer for accurate characterization of ultrathin dielectric films. Optical tunnelling mimics the absorption in metallic films, enabling accurate measurement of the refractive index of ultrathin dielectric film. A regression model shows that a refractive index resolution of 0.001 for films as thin as 1 nm is possible. A solid-immersion nano-ellipsometer that incorporates this near-field ellipsometric technique with a solid-immersion lens is constructed to demonstrate the viability of this technique. Such a nanoellipsometer can accurately characterize thin films ranging in thickness from subnanometre to micrometres with potential transverse resolution of the order of 100 nm.
- Optical tunnelling
- Solid immersion
- Ultra-thin film characterization